This application relates to and claims priority from Japanese Patent Application No. 10-204880 filed on Jul. 21, 1998, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to die release lubricant applied to an inside surface of a die for casting of metal such as aluminum.
2. Related Art
Conventionally, when metal such as aluminum is casted with a die (i.e., metal die), die release agent and lubricant are applied to an inside surface of the die so that molded metal is smoothly released from the die and a plunger for pushing melted metal into the die smoothly moves.
However, the conventional die release agent and lubricant are substantially composed of oil or water soluble fat and oil. Therefore, the conventional die release agent and lubricant applied to the die are decomposed due to heat of melted metal and the die during casting, and generate a relatively large amount of thermal decomposition gas. The generated thermal decomposition gas may be taken into the molded metal and cause various defects such as a shrinkage cavity and wrinkling. As a result, quality of the molded metal is declined.
Some of the conventional die release agent and lubricant include an inorganic compound dispersed into water. However, in this case, since water is not dried quickly, water is decomposed (evaporated) due to heat of the melted metal during casting. As a result, the above-mentioned defects of the molded metal occur.
JP-A-4-279244 discloses powder die release agent made by mixing powder or granule die release base material composed of an inorganic compound and another organic or inorganic compound. In the powder die release agent, both the die release base material and the organic/inorganic compound are made into powder or granule, or the die release base material is covered by the organic/inorganic compound.
However, when the powder die release agent is applied to an inside surface of a die, the powder die release agent tends to be scattered due to air flowing around the die. As a result, application efficiency and a working environment are worsened. Further, the powder die release agent has poor dispersibility and may be ununiformly applied to the surface of the die.
An application amount of the powder die release agent may be increased so that the powder die release agent is uniformly applied to the surface of the die. However, in this case, an amount of thermal decomposition gas generated from the powder die release agent during casting is also increased. As a result, the molded metal may have defects such as the shrinkage cavity and wrinkling, and quality of the molded metal is declined.
In view of the foregoing problems, it is an object of the present invention to provide die release lubricant which is uniformly applied to an inside surface of a die and generates an extremely little amount of thermal decomposition gas while improving application efficiency.
According to the present invention, die release lubricant includes powder solid lubricant, adhesion enhancer made of organic or inorganic compound and volatile solvent. The die release lubricant is applied to an inside surface of a die before melted metal is injected into the die for casting. The die release lubricant is in a liquid state and is uniformly applied to the inside surface of the die. Therefore, an application amount of the die release lubricant is reduced, thereby reducing thermal decomposition gas generated from the die release lubricant during casting. As a result, the molded metal has almost no defects such as a shrinkage cavity and wrinkling and has excellent quality. Furthermore, the die release lubricant is less scattered during application in comparison with conventional powder die release agent. As a result, application efficiency and a working environment are improved.
Preferably, the powder solid lubricant has an average particle radius of 0.1-10 xcexcm, and includes particles having a radius of smaller than 0.1 xcexcm at less than 5% by weight, and particles having a radius of larger than 10 xcexcm at less than 5% by weight. As a result, application uniformity of the die release lubricant is improved.
More preferably, a weight ratio of the adhesion enhancer to the powder solid lubricant is in a range of 0.05/100 and 15/100. As a result, adhesion strength of the die release lubricant is increased.
More preferably, the volatile solvent has a boiling point of 40-150xc2x0 C. and a firing point of 250xc2x0 C. or higher. As a result, the volatile solvent is immediately volatized when the die release agent is applied to the die, and the powder solid lubricant is quickly and firmly adhered to the die with the adhesion enhancer.